Fastener driving machine



March 23,1943. I POLZER I 2,314,847

FA'STENER DRIVING MACHINE Filed Dec. 20, 1940 4 Sheets-Sheet 1 INVENTORATToRNE'Ys March 23, 9.43.

'- F. POLZER FASTENER DRIVING MACHINE Filed Dec. 20, 1940 v 4Sheets-Sheet 2 ATTORN EY5 March 23, 1943. F. POLZER FASTENER DRIVINGMACHINE Filed Dec. 20, 1940 4 Sheets-Sheet 3 ATTORNEYS.

arch 23, 1943'. POLZEfi FASTENER DRIVING MACHINE Filed Dec. 20, 1340 4sheets sheet 4 ATTORNEYS Patented Mar. 23, 1943 FASTENER DRIVINGIVIACHINE Fridolin Polzer, Norwalk, Conn., assignor to The E. H.Hotchkiss Company, Norwalk, Conn, a corporation of Connecticut IApplication December 20, 1940, SerialNo. 371,011

12 Claims.

This invention relates to a fastener driving machine of the type inwhich a spring is used for driving the plunger to set the fastener, andhas for an object to provide a construction in which if it is desired tochange the driving power, as for example to increase the driving power,the spring may be easily and quickly changed with a simple operation toeither provide a heavier or lighter spring as desired.

It is also an object to provide a construction in which as the operatinghandle is depressed there is no increase in pressure required on thishandle as it moves toward the end of its movement, but a substantiallyuniform pressure will operate the handle throughout this entiremovement, or the pressure required may even be lighter at the end thanat the beginning of its movement as contrasted with old types ofmachines where the pressure required to operate the handle and compressthe spring increases as the spring is compressed.

It is another object to provide a construction in which substantiallyall of the parts maybe stamped and formed from sheet metal.

It is a further object of the invention to pro- C vide a device in whichthe same mechanism may be used to drive various types of fasteners suchfor example as two-pronged staples, tacks, nails and the like, it beingnecessary for the different types of fasteners to merely change theshape and size of the fastener guiding and feeding means and the drivingplunger to suit the type and size of fastener used.

With the foregoing and other objects in view I have devised aconstruction as illustrated in the accompanying drawings forming a partof this specification. It is however to be understood that I am notconfined to the specific construction and arrangement shown but mayemploy various changes and modifications within the scope of theinvention. In these drawings:

Fig. l is a side elevation of my improved fastener driving machine withparts broken away to more clearly show the construction;

Fig. 2 is a front elevation thereof with parts broken away to moreclearly show the construction;

Fig. 3 is a bottom plan view of the device;

Fig. 4 is a transverse vertical section substantially on line 44 of Fig.1;

Fig. 5 is a vertical longitudinal section showing the parts in theirnormal positions;

Fig. 6 is a front elevation showing the securing means for the yokereleased to permit exchange of the driving spring;

Figs. 7, 8 and 9 are detailed sections substantially on lines 1-1, 8--8and 9-9 respectivelyof Fig. 5;

Fig, 10 is a partial side elevation and partial vertical longitudinalsection showing the operating handle depressed and the elements in thepositions they occupy just prior to the release of the plunger for thefastener driving operation;

Fig. 11 is a detailed section substantially on line ll-l! of Fig. 10with the side plates of the outer housing omitted;

Fig. 12 is a side elevation, with parts broken away to more clearly showthe construction of the operating unit for raising the plunger tocompress the driving spring prior to the fastener driving operation;

Fig. 13 is a front elevation thereof looking as indicated by line I3l3of Fig. 12 v Fig. 14 is a rear elevation and section looking asindicated by line I4I4 of Fig. 12;

Figs. 15, 16 and 17 are a bottom plan view, front elevation and sideelevation respectively of the plunger for carrying and operating thedriver for the fastener, parts of Fig. 16 being broken away to moreclearly show the construction;

Fig. 18 is a side elevation looking toward'the inner side of one of theside plates of thebody housing; 7

Figs. 19, 20, 21 and 22 are detail sections substantially on lines I9l9, 28-20, 2|-2| and 22 22 respectively of Fig. 18;

Fig. 23 is a top plan View of the support for staple fasteners andcarrying them to driving position;

Fig. 24 is a side elevationthereof;

Fig. 25 is a front end view of the fastener support of Figs. 23 and 24;

Fig, 26 is a transverse section substantially on line 26-26 of Fig. 24.;

Figs. 2'7 and 28 are a front and side elevation respectively of thefront portion of a strip of staple fasteners which may be used in thismachine;

Fig. 29 is a top plan view of a horizontal dividing and spacing wallbetween the side plates of the housing and forming a cover over thestaple guiding support; and

Fig. 30 is a side elevation of one end portion thereof.

The device is illustrated as adapted for driving substantially U-shapedor two-pronged staples or staple fasteners, but as above indicated thesame mechanism may be employed for driving other types of fasteners,such for example as other types of staples, tacks and nails, it beingnecessary merely to change the shape or form and size of the fastenersupport and guiding means and the driver for the fastener to correspondwith the type and size of fastener used. Also the device is shown fordriving the staple fastener directly into the article to be fastenedwithout clinching and is therefore what is known as a tacker, but it maybe used with a base carrying an anvil in alignment with the stapledriver for bending over and clinching the staple prongs as in the typeof machine known as a stapler, such base and anvil not being shownhowever in the drawings as they may be of a conventional type.

The device comprises a body including two spaced side plates l and 2forming a main or outer housing. These plates are preferably stamped andformed from sheet metal of proper gauge and are made substantially thesame except that they are right and left hand, or each is reversedwith'respect to the other, the right hand plate 2 being shown in detailin Figs. 18 to 22. The main body of each of these plates is providedwith an elongated opening 3, and when the plates are assembled inupright parallel spaced relation these openings are in alignment forpassage of the fingers of the operator and form the lower part of thegrip on the machine. The front part of the plate is offset as indicatedat 4 to provide one-half of a guide for a vertically movable plungercarrying the staple driver 6. The other plate I is similarly offset inthe opposite direction as indicated at 1 to complete the other half ofthe vertical guide for the plunger. The rear edges of each of theseoffsets may have an ear 8, the two being side by side and may be securedtogether by any suitable means such as a screwor rivet 8a or by welding.

The plunger ;5 which is guided for vertical movement in the guidewayformed by the offsets 4 and I has a substantially rectangular headportion 9 and a stem In providing a shoulder 9a. The head portion isrecessed on its lower front face as indicated at -l I to receive theupper end of the driver B, and in the wall of this recess is anotherrecess I2 to receive a lug l3 cut and bent backwardly from the driver toconnect the driver to the plunger sothat the driver will be carriedupwardly with upward movement of the plunger. The shoulder l4 at the topof the recess ll engages the upper end of the driver so as to force thedriver downwardly to drive the fastener as the plunger is drivendownwardly under action of a spring l5 as will later be described. Thisspring embraces the stem l9 and rests at its lower end on the shoulder9a. At its upper end it engages the under side of the top wall I6 of ayoke IT. This yoke may also be stamped and formed from sheet metal andhas side arms I 8 extending downwardly from the top wall 16 on oppositesides of the plunger guide portions 4 and 1 of the body. On the outerwalls of each of these guide portions 4 and 7 there is a downwardlyextending hook or lug l9 cut from the walls of the guide and forcedoutwardly therefrom so as to pass through opening 28 formed in thecorresponding arm [8 of the yoke, and by engaging over the lower edge ofthis opening as shown in Figs. 1 and 2 retaining the yoke in position onthe body. The yoke may be easily removed by forcing it downwardlyagainst the action of the spring l5, which can be done by pressure ofthe hand on top of the yoke, until the walls of the arms l8 under thehooks 19 are released therefrom permitting the arms to spring outwardlyas indicated in Fig. 6. This releases the arms, and the yoke may then bereadily lifted from the body.

At the lower end of each of the arms 18 is an inwardly extending lug 2!each passing through an opening 22in the outer side wall of the offsetguide portions 4 and I. These extend into the guideway for the plungerover the top of a resilient; cushioning bumper 23 under the plunger toarrest downward movement of the plunger and cushion the blow. Thisbumper may be of various constructions but that shown comprises acentral rubber plug 24 embraced by a heavy spring 25. This bumper issupported on a transverse wall 26 mounted in the lower part of theguideway. In the present construction this wall is a block having lugs21 extending into and seated in openings 28 formed in the walls 4 and 1whereby the block 26 is supported. It has a notch or recess 2% (Fig. 7)in its front .edge for passage of the driver 6. The lugs 2| by extendinginwardly over the bumper prevent the bumper from moving upwardly in theplunger guideway so that it is retained in proper position on the wall25. The head 9 of the plunger is provided with grooves 29 to formclearance for the lugs 2| and permit the plunger to move downwardly bythese lugs. The top wall N5 of the yoke extends downwardly on the frontand rear sides of the plunger guideway as shown at 30 to help retain theyoke in position.

Between the side plates 1 and 2 and at the lower portions thereof is astaple support and guide 3|. This may be a solid bar but is preferablyformed of sheet metal and substantially U- shaped in cross section asshown in Figs. 4, 8 and 275.. The staples 32, preferably in a connectedstrip 33, are supported on this support and guided thereby to the stapledriving position, the staple strip being inserted on the sup portthrough the right hand or rear end of the housing as viewed in Figs. 1and 5. This support is the general shape of the inner part of the stapleand as the staple 32 shown is tapered, that is the prongs are inclinedinwardly so that the free ends of the prongs are closer together at thebottom of the staple than at the connected portion at the top as shownin Fig. 2'7, the side walls of the support 3| are also inclined tocorrespond. This retains the staples on the support and prevents theirfalling or rising off the top thereof. This support and guide will ofcourse be of a size and shape to correspond with the staple or otherfastener for which the machine is designed to be operated.

These staples are fed along this support by means of a follower 34 ofsubstantially inverted U-sha-pe to slide along the top of the support 3|with its side wall embracing this support as shown in Fig. 8. At itsforward end the follower may have a downwardly extending lip 34a betweenthe sides of support 3| to engage the top or cross member of the staplesand insure these staples do not ride onto the top of the follower. Thisfollower is provided with a loop 35 embracing and slidable on a rod 35located between the sides of the support 31 and on which is a coilspring 31 tending to shift the follower 34 forwardly along the support3! to feed the fasteners forwardly to the driving position. The end ofthe rod may be flattened at 36a to make it wider to prevent the loop 35sliding off the end of the rod. At the rear end the rod 36 is bentupwardly and forwardly as shown at 38 to provide a hook 39 adapted tohook into an opening 40 at the rear end of the member 4| forming a topwall or cover over the support 3I and extending transversely between theplates I and 2. It forms a spacing element between the plates and helpsto them in proper relation. At its edges this member 4| has lugs 42extending into openings 43 in the plates I and 2 to position the platesI and 2 and member 4! in proper relation to each other and also supportthe member M. This member 4I also has downwardly extending flanges Mo onthe opposite side edges to rest on the lower edges 44 of the openings 3in the plates I and 2 and to extend downwardly on the outer sides ofthese plates as shown in Figs. 1 and to hold the plates againstseparation and also to form a finish at the lower sides of the openings.By lifting the hook 39 from the opening the follower 34 may be withdrawnfrom the rear end of the support 3I to permit insertion of a strip ofstaples onto this support. Then the follower may be replaced and thehook 39 inserted in the opening 48.

The staple support and guide 3! is mounted on the lower member 45 whichis substantially channel or U-shape, and the member 31 is secured at itslower wall on the bottom wall of this member by any suitable means suchas rivets 46, spot welding, or the like. The outer side flanges 4'!embrace the lower edges of the side plates I and 2 and the bottom wall45 has elongated openings 48 therein to receive lugs or projections 49projecting downwardly from the lower edges of the plates I and 2 toproperly position the member 45 and support BI with relation to the sideplates I and 2 and the other elements of the device.

These lugs 49 or the plates I and 2 near them are secured to the sideflanges 41 of the bottom member 45 by suitable means such as rivets orwelding 49a.

At the forward end of the support 3% there is mounted an L -shapedmember having an upright wall 50 between the sides of the member 3| andforming the rear wall of a guideway or raceway 5I for passage of thestaples under the action of the driver 6. This member is mounted bymeans of its lower wall 52 seating on the bottom wall 3Ia of the member3| and secured thereto by any suitable means such as rivets 53 or bywelding. The wall 50 may be supported against backward movement by meansof lugs 50a1anced from the side walls of support 3! and bent inwardly toengage the rear side of wall 50 and support it as shown in Figs. 5, 23and 24. The front wall of the raceway 5I is formed by a removable plate54. This plate has its opposite vertical side edges bent backwardly andinwardly to form flanges 55 (Fig. 9) embracing outwardly extendingflanges 56 on the forward edges of the side plates I and 2 and below theoffset plunger guide portions 4. Spacing plates 51 may be secured tomember 54 and placed between the plate 54 and the flanges 6 at oppositesides of the driver 56 to give a proper spacing of the front wall of themember 58 from the guide wall 59 to form the raceway 5! for passage ofthe staples and the driver 5. The member 54 is placed in position bymerely sliding it upwardly on the flanges 55 from the lower endsthereof, and it is held in position by any suitable means such as aspring plate or finger 58 secured to the front wall of the offsets 4 byany suitable means such as rivets 59 and overlapping the member 54. Alug 65 cut and bent backwardly from the spring plate 58 may seat in arecess in the front wall of the member 54 to form a catch to retain themember 54 in position. By merely lifting the lower end of spring 58outwardly, this catch may be released and the member 54 slid downwardlyout of position to give access to the front end of the staple supportand the lower portion of the driver 6, and also to permit removal of anystaple which may become jammed in the raceway. The forward end of thebottom wall 45 may be beveled as shown at 45a (Figs. 23, 24 and 25) toprevent backwardly inclined staple prongs from jamming on this wall and.for guiding such prongs into the raceway 5 I.

The means for lifting the plunger against the action of the spring I5 tocompress this spring and also to raise the driver 6 to permit a fastenerto be fed into the raceway under this driver in position to be driventhereby is mounted and assembled as a separate unit, which unit is shownin Figs. 12, 13 and 14 removedfrom the machine, but is shown inassembled relation in the machine in Figsr5 and 10. This unit assemblycomprises an inner housing BI of general U-shape having side walls 62and a bottom wall 63 connecting the lower edges to the side walls. Thismay also be formed of sheet metal of suitable gauge or thickness andbent to shape. Pivoted between the sides of this housing adjacent theupper edges thereof and on the pivot pin 64 is an operating handle 65.This handle is also formed from sheet metal and is of generally channelor inverted U-shape in cross section, and the side walls at the forwardend thereof are extended downwardly from the pivot I54 to for a leverarm 66. At the lower end of this arm and mounted between the side wallsthereof is a roller 6! mounted on a suitable cross pin 58. The two sidesof the lever .arm 66 extend on the opposite sides of and embrace a camlever 69 pivoted between the sides 52 of the housing on the pivot '10rearwardly of the .pivot 64, and the lower edge 'II of this cam lever isshaped to form a suitable cam surface contacting and cooperating withthe roller 61.

Embracing the forward end of this cam lever; 69 is a pawl I2. This pawlis of general channel shape in cross section with its side walls 13embracing the front end of the lever 59 and pivoted thereto adjacent itslower end by means of the pivot pin 14. This pawl 52 is located betweenthe side walls 62 of the inner housing. The top end of its front wall I5may engage under a downwardly facing shoulder 15 formed on the rear wallof the plunger 9 to lift the plunger when the pawl is lifted, as willpresently be described. A spring 11 mounted in a recess in the forwardend of the cam lever and embracing a stud IE on the pawl tends to shiftthe upper end of the pawl, outwardly or forwardly about the pivot 14.The upper edges of the side walls 13 are inclined to form a cam 18 toengage a cross pin 19 mounted in and extending between the side walls 52of the inner housing to shift the upper end of the pawl 12 backwardlywhen it approaches the end of its upward movement and thus to withdrawthe upper end of the wall 15 from under the shoulder 15 on the plungerto release the plunger to permit it and the driver 6 to be forceddownwardly is provided projecting beyond the sides 13 of the pawl intoslots 8| in the side walls 62 of the inner.

housing, and by engaging the front or forward edges of these slots limitthe forward movement of the pawl.

Also to assist in preventing catching of the plunger on the pawl thelower rear edge of this plunger may be inclined or chamfered as shown at82. A spring 83 is coiled about the pivot 64 and has one end 84 pressingon the under side of the lever 65 and its other end 85 resting in agroove 86 on top of the cam lever 69. This spring therefore tends toraise the hand lever 65 upwardly about the pivot 64 and to swing the camlever 69 downwardly about its pivot 10.

When the lever 65 is depressed the roller 61 is forced to the left asviewed in Fig. and runs along the cam surface II. This raises the freeend of the cam lever 69 about its pivot and thus raises the pawl 72.this pawl is engaged under the shoulder 16 on the plunger 9 it raisesthis plunger and with it the driver 6 and compresses the spring l5. Thecam H is so shaped that as the roller 61 runs along this cam when thehand lever 65 is depressed this roller moves away from the pivot 10 ofthe cam lever. Therefore the greater the lever 65 is depressed thefarther the roller 61 and its point of engagement with the cam surfacebecomes spaced from the pivot 19. It will thus be seen that as the leveris depressed its leverage on the cam lever 69 through the roller 67increases or becomes greater as the spring I5 is compressed. Thus thefarther the lever 65 is depressed the greater will be the leverage onthe cam lever 69 and therefore the cam H can be designed to cause thisincrease in leverage to compensate for the increase in the resistance ofthe spring I5 as this spring is compressed. The cam H can be made sothat as the operating lever 65 is depressed there is no increase inpressure required as it approaches the lower extreme of its movement. Infact the cam H can be so designed if desired, that the pressure requiredto operate the lever may decrease as the lever is operated. The shape ofthis cam also determines the travel or throw of the plunger and the camcan therefore be designed to give a greater or less movement to theplunger in relation to the movement of the operating handle as desired.It will also give a relatively long throw to the plunger with a shortstroke of the operating handle.

To give a more comfortable grip, a resilient or soft rubber pad 81 maybe mounted on the top of the lever 85 and secured thereto by anysuitable means such as rivets 83. Another soft rubber pad 89 may bemounted between the side plates l and 2 of the body at the upper part ofthe openings 3 and secured in position by any suitable means such aspins or rivets 90.

The removable unit assembly including the inner housing 6| may bemounted in the outer housing between the body plates I and 2 as shown inFigs. 5 and 10 and secured therein by any suitable means such as thescrews or rivets 9! extending transversely through the side members ofthe two housings. By removing these securing means 9| this operatingassembly as shown in Figs. 12, 13 and 14-. may be removed as a unit fromthe body or outer housing as shown in dotted lines Fig. 1.

In operation the operator grips the device by passing his fingersthrough the openings 3 under and engaging the grip pad 89 and with thepalm of the hand resting on top of the operating lever 55. Then aftersetting the lower edge of the de- As the upper edge of vice on thearticle to be fastened the lever may be depressed to the position shownin Fig. 10. This operation through the action of the roller 6! on thecam H raises the forward end of the cam lever 69 about the pivot 19.This raises the pawl 12 and as the forward upper edge of this pawlengages the shoulder on the plunger 9, it also lifts this plungeragainst the action of the spring l5, thus compressing the spring and'storing energy in it. Upward movement of the plunger also carries withit the driver 6, and as the lower end of this drives passes above thetop of the staple support 3| and the strip of staplesthereon, this stripis fed forwardly by the follower 34 to carry the forward staple 3211(Fig. 10) into the driving position in the raceway 5| and under thelower end of the driver 6. As the lever 65 is further depressed from theposition of Fig. 10 the pin l9 acting on the cam 18 on the pawl '12moves the upper end of this pawl to the right or rearwardly withdrawingthe upper edge of this pawl from the shoulder 16 on the plunger. Thisreleases the plunger whereupon the spring l5 forces it downwardly with aquick action carrying with it the driver 6. This driver forcesdownwardly the forward staple 32a and drives it into the work to befastened. The downward movement of the plunger is arrested by its lowerend striking the top of the bumper 23 as shown in Fig. 5. This being aresilient bumper also cushions the force of the blow preventingobjectionable blows or hammer action on the other elements of themechanism. After the fastener is driven release of pressure on thehandle 65 permits it to be raised under the action of the spring 83returning the parts to the position of Fig. 5. This permits the camlever 58 and the pawl l2 carried thereby to be moved downwardly by theirown weight and action of the spring arm 85 and cause the forward upperedge of the pawl to pass below and engage under the shoulder 16 on theplunger in position for again lifting the plunger on depression of theoperating lever 65 for setting another fastener.

It will thus be seen that the device can be made principally of partsstamped and formed from sheet metal, decreasing the weight of the deviceand increasing its strength for the amount of metal used. Also that itwill not be as fatiguing to operate as older types of fastener drivingmachines where the pressure required to operate the operating leverincreases with movement of this lever, but that in this device thepressure required to operate the lever does not increase and may evendecrease toward the end of its movement. If more driving power isdesired all that is necessary is to remove the yoke I1, remove the oldspring and insert a new and stronger spring, or any other spring of thedesired power.

Having thus set forth the nature of my invention, what I claim is:

1. A fastener driving machine comprising an outer housing includingspaced side plates, a guideway at the front of the housing, a verticallyreciprocable driver and support in said guideway, a spring for forcingthe driver downwardly to drive a fastener, means for feeding fastenersto a driving position under the driver, and means for lifting the driveragainst the action of the spring preparatory to the driving operationcomprising a unit assembly mounted between the side plates including aninner housing, an operating lever pivoted in the inner housing andhaving a depending arm, a cam lever pivoted in said latter housing andhaving a cam on its lower edge,

'means on the-depending arm to run on said cam 'to lift the cam lever,and means on the cam lever ;to engage the driver support to lift thedriver.

2. Afastener driving machine comprising an 'outer housing includingspaced side plates, a

guideway at the front of the housing, a vertically reciprocable driverand support in said guideway, a spring for forcing the driver downwardly-to drive a fastener, means for feeding fasteners to a driving positionunder the driver, a unit assembly comprising an inner housing, anoperating lever and a cam lever mounted in said latter housing, said camlever having a cam on one edge, means carried by the operating lever.running on said cam to lift the cam lever, a pawl carried by the camlever, and means for mounting the unit assembly in the first housingwith the pawl in position to engage the driver support to lift saiddriver against the action of the way, a spring for forcing the driverdownwardly to drive a fastener, means for feeding fasteners to a drivingposition under the driver, a unit assembly comprising an inner housing,a hand lever and a cam lever mounted in said latter housing, said camlever having a cam on the lower edge thereof, said hand lever having adepending arm carrying a roller to run on said cam to life the camlever, a pawl pivoted at the free end of the cam lever, spring meanstending to return the two levers to normal position, and means formounting the unit assembly in the first housing with the pawl inposition to engage the driver support to lift said driver against theaction of the first spring.

4. A fastener driving machine comprising a housing having an uprightguideway, a driver and its support in said guideway, said support havinga downwardly facing shoulder, a spring for forcing the driver downwardlyfor driving a fastener, means for feeding fasteners to the drivingposition under the driver, a hand lever pivoted in the housing, a secondlever, cooperating means on the hand lever and second lever for liftingthe latter lever on depression of the hand lever, a pawl substantiallyU-shape in cross section embracing the free end portion of the secondlever, means for pivoting theside walls of the pawl to the lever, theupper end of said pawl being adapted to engage said shoulder to lift thedriver, a cam on the pawl, and cooperating means to engage said cam toshift the pawl from said shoulder as the hand lever approaches its lowerlimit of movement.

5. A fastener driving machine comprising a housing having an uprightguideway, a driver and its support in said guideway, said support havinga downwardly facing shoulder, a spring for forcing the driver downwardlyfor driving a fastener, means for feeding fasteners to the drivingposition under the driver, a unit assembly including an inner housing, ahand lever pivoted in the latter housing, a second lever pivoted in saidhousing, cooperating means on said levers for raising the second leveron depression of the first lever, a pawl pivoted on said second leverand adapted to engage said shoulder to raise the driver, a springtending to swing the pawl outwardly into alignment with said shoulder,said inner housing having a slot in a side wall thereof, a projection onthe pawl extending into said slot "and adapted to engage an edge thereofto limit outward movement of the pawl, and cooperating means on the pawland housing to remove the pawl from said shoulder as the hand lever approaches the limit of its downward movement.

6. A fastener driving machine comprising a housing having an uprightguideway open at the tending resilient arms on opposite sides of theguideway, means for detachably connecting said yoke to the housingcomprising downwardly opening hooks on the outer walls of the guidewayand openings in the arms to receive said hooks, operating means forraising the driver against action of said spring preparatory to drivinga fastener, and means for feeding fasteners to the driving positionunder the driver.

'7. A fastener driving machine comprising a housing having an uprightguideway open at the top, a driver and its support mounted in theguideway for reciprocating movement, a spring for moving the driverdownwardly for driving a fastener, a removable yoke having a wall overthe open top of the guideway and forming an abutment for said spring,said yoke having downwardly extending arms embracing opposite sides ofthe guideway, downwardly opening hooks on the outer walls of theguideway, said arms having openings to receive the hooks and engageunder them under action of the spring to retain the yoke on the housing,means for raising the driver preparatory to driving a fastener, andmeans for feeding fasteners to driving position.

8. A fastener driving machine comprising a housing having an uprightguideway open at the top, a driver and its support mounted in theguideway for reciprocating movement, a spring for moving the driverdownwardly for driving a fastener, a removable yoke having a wall overthe open top of the guideway and forming an abutment for said spring,said yoke having downwardly extending arms embracing the opposite sidesof the guideway, means for detachably securing said arms to the housing,a supporting wall at the lower part of the guideway, a resilient bumpersupported on said wall to receive the blow of said support and limit itsdownward movement, said arms having lugs extending inwardly throughwalls of the guideway to a position over the bumper to limit upwardmovement of the bumper, means for raising the driver preparatory todriving afastener, and means for feeding fasteners to the drivingposition.

9. A fastener driving machine comprising a housing having an uprightguideway open at the top, a driver and its support mounted in theguideway for reciprocating movement, a spring for moving the driverdownwardly for driving a fastener, a removable yoke having a wall overthe open top of the guideway and forming an abutment for said spring,said yoke having downwardly extending arms embracing opposite sides ofthe guideway, downwardly opening hooks on the outer walls of theguideway, said arms having openings to receive the hooks and retain theyoke on the housing, a supporting wall at the lower part of theguideway, a resilient bumper supported on said wall to receive the blowof said support and limit its downward movement, said arms having lugsextending inwardly through walls of the guideway to a position over saidbumper, means for raising the driver preparatory to driving a fastener,and means for feeding fasteners to the driving position.

10. A fastener driving machine comprising a housing having a guideway, adriver and its support reciprocable in said guideway, a spring forshifting the driver to set a fastener, a supporting wall in theguideway, a resilient bumper on said wall to receive the blow of thesupport and limit its movement and comprising a resilient rubber coresurrounded by a coiled spring, means for retracting the driver againstaction of the first spring preparatory to a driving operation, and meansfor feeding fasteners to driving position in front of the driver.

11. A fastener driving machine comprising a housing having an uprightguideway open at the top, a driver and its support mounted in theguideway for reciprocating movement, a spring for moving the driverdownwardly for driving a fastener and removable through the top of theguideway, a removable yoke including a wall over said open top of theguideway forming an abutment for said spring and downwardly extendingarms at the opposite sides of the guideway, means for detachablysecuring the yoke to the housing comprising downwardly opening hooks onthe walls of the guideway and openings in said arms to receive saidhooks and engage at their lower edges under the hooks under action ofthe spring to retain the yoke in place, and said yoke being shiftabledownwardly against action of the spring to release the arms.

12. A fastener driving machine comprising a housing having an uprightguideway open at the top, a driver and its support mounted in theguideway for reciprocating movement, a spring for moving the driverdownwardly for driving a fastener and removable through the top of theguideway, a removable yoke including a wall over said open top of theguideway forming an abutment for said spring and downwardly extendingresilient arms at the opposite sides of the guideway, downwardly openinghooks on the walls of the guideway, said arms having openings to receivesaid hooks and engage at their edges under the hooks under action of thespring to retain the yoke in place, said yoke being shiftabledownwardlyagainst action of the spring, and said arms tending to spring outwardlyso that when the yoke is thus shifted downwardly the arms will moveoutwardly away from the hooks to release the yoke.

FRIDOLIN POLZER.

